The present invention relates to an agricultural combine; and more particularly, it relates to apparatus for leveling the frame of a hillside combine as the harvester traverses an inclined or sloped area.
There are combines capable of traversing an inclined or sloped area while maintaining the combine frame level. The purpose of leveling a combine is that the internal mechanism for processing the crop and separating the seed stays in a level position at all times. This has the advantage that the various functioning parts of the combine, such as the cylinder, augers and cleaning shoe are level at all times and the distribution of grain in those devices is uniform. This has the effect of making the functioning parts of the combine operate more efficiently and more accurately.
One such prior system uses a walking beam axle in the front and rear of the combine and independent spring suspension at each wheel in order to operate properly. In some cases, the walking beam axle may be replaced by vertically oriented hydraulic cylinders arranged so that as one cylinder extends to raise one side of the combine relative to the axle, the complementary cylinder retracts to lower the other side of the combine.
The present invention employs hydraulic cylinders for leveling the combine frame. The invention may be operated manually by the operator or it may be under control of a level-sensing mechanism. It also has the advantage that it may be adapted to retrofit existing combines which are not hillside combines but have a hollow front axle.
The present invention uses left and right side wheel linkages interposed between the front left and right wheels of the combine. Preferably, the wheel linkages are four-bar linkages so that if the front axle is horizontal, the wheels remain vertical for all adjusted positions. The rear axle may be connected to the main frame by a pivot connection at the mid-point of each so that if the front axle is horizontal, the entire frame will likewise be horizontal.
First and second hydraulic cylinders are connected between the mid-point of the front axle and the respective wheel linkages. These cylinders may be controlled either from the operator's position by the operator or by a level-sensing switch automatically if desired, as will be better understood from the detailed description given below.
The illustrated wheel linkages are four-bar linkages with two vertical and two horizontal links. One of the horizontal links is in the form of a crank, and that link is connected to the rod end of an associated hydraulic cylinder. The other horizontal link of the wheel linkage, sometimes referred to as a "control" link, is pivotally connected to the corresponding control link of the wheel linkage for the other wheel by means of a connecting rod or tie rod. In the case of retrofitting at least one manufacturer's combine from a level-land combine to a hillside combine, the tie rod interconnecting the control links of the wheel linkages may extend through the horizontal front axle of the combine. This reduces the expense of such a modification.
In operation, as one hydraulic cylinder is retracted, it cranks its associated wheel linkage to lift the tire which that linkage supports. The other hydraulic cylinder extends to crank its associated wheel linkage in a counter direction, thereby lowering its associated wheel. When two hydraulic cylinders are used, the tie rod between the control links on the wheel linkages acts as a synchronizing mechanism so that the upward displacement of the first wheel relative to the axis of the axle is substantially equal to the downward displacement of the other wheel. If only one hydraulic cylinder is used, the tie rod may be used to actuate the corresponding control link on the other side of the axle, also serving to insure that the amount by which one wheel is raised is substantially equal to the amount by which the other wheel is lowered, thereby maintaining the front axle in a generally horizontal disposition.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.